This section provides background information related to the present disclosure which is not necessarily prior art.
AT 403 213 B discloses a capacitive humidity sensor including a square-wave generator whose signal is supplied to an AND gate via two different signal paths, wherein one signal path extends directly and the other includes a measuring electrode whose capacitance influences the signal shape and thereby delays the reaching of a switching threshold.
WO 2007 025 785 A1 discloses a capacitive sensor comprising a square-wave generator whose signal is supplied via two different signal paths to a XOR gate, wherein one signal path includes a measuring electrode and the other a reference electrode.
DE 10 2012 106 526 A1 discloses a capacitive door handle sensor for a motor vehicle comprising at least two electrodes with different monitoring areas, wherein one electrode acts as a reference electrode.
DE 10 2012 224 007 A1 discloses an arrangement and a method for determining the capacitance of a measuring capacitor by means of a voltage detectable with an analog-to-digital converter comprising a charge transfer device for transferring the charge of an unknown capacitance Cx to a measuring capacitor CL, wherein, however, only the comparison of a single unknown capacitance Cx with a reference capacitance Cref is provided.
DE 10 2014 216 998 A1 shows an evaluation circuit for a capacitive sensor comprising a plurality of measuring capacitances and a reference capacitance, wherein the measuring capacitances are successively compared in a predetermined time regime with the same reference capacitance.